Weather radars, for example, are used to detect the intensity of echoes reflected by precipitation particles of clouds, rain, and the like, and to observe or forecast the state of weather. Recently, in addition to radars that use only the conventional horizontally polarized waves, dual polarization radars have been used, which emit pulse waves of horizontally polarized waves and vertically polarized waves alternately, and observe the shape, size, and the like of an observation target based on difference in intensity of reflection from the observation target.
In the case of observation using radars, signals from other radar sites, for example, may be mixed into the received signals as interference waves. Further, multipath interference may occur and unnecessary signals may be mixed into the received signals. As a technique of removing such interference waves, “Metrological Agency, ‘Doppler Radar for Airport Weather Manufacturing Specification (Kagoshima Airport)’, May 2006, p. 19” discloses a technique of replacing IQ data judged as including interference waves with IQ data of a hit before.